Installation for programmed control of a machine-tool

ABSTRACT

Installation for programmed control of a machine tool of the type comprising, for each carriage, a mechanism for controlling the drive linked to a motor and a system for controlling the supply to said motor, said installation including: means for the detection of approach having a relatively average accuracy of the order of 0.3 mm., by default, said approach detection means being capable of covering on their own the total extent of travel of the carriage; and means for the detection of stopping having a relatively high accuracy of the order of 0.02 mm.; and wherein said system for controlling the supply to said motor is connected through appropriate connecting means to selectively be commanded by said approach detection means, the information supplied by said approach detection means causing the supply of current to said motor to change so as to slow down said motor to a constant minimum speed and at the same time conditioning said connecting means so that said supply control system is put under the control of said stop detection means, the information supplied by said stop detection means subsequently causing cutting off of said supply to the motor in order to ensure the precise stopping of said carriage.

United States Patent [72] Inventor Jacques Prodel 13 rue Michelet, Rueil-Malmaison, llautsde-Seinc 92, France [2 l Appl. No. 793,092

[22] Filed Jan. 22, 1969 [45] Patented June 22, I971 [32] Priority Jan. 23, 1968 [33] France [54] INSTALLATION FOR PROGRAMMED CONTROL Primary ExaminerBenjamin Dobeck Atlorney.lacobi, DavidsornLilling and Siegel ABSTRACT: installation for programmed control of a machine tool of the type comprising, for each carriage, a mechanism for controlling the drive linked to a motor and a system for controlling the supply to said motor, said installation including: means for the detection of approach having a relatively average accuracy of the order of 0.3 mm., by default, said approach detection means being capable of covering on their own the total extent of travel of the carriage; and means for the detection of stopping having a relatively high accuracy of the order of 0.02 mm.; and wherein said system for controlling the supply to said motor is connected through appropriate connecting means to selectively be commanded by said approach detection means, the information supplied by said approach detection means causing the supply of current to said motor to change so as to slow down said motor to a constant minimum speed and at the same time conditioning said connecting means so that said supply control system is put under the control of said stop detection means, the infonnation supplied by said stop detection means subsequently causing cutting off of said supply to the motor in order to ensure the precise stopping of said carriage.

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" sum 1a or 14 Iuve/uwm- J/ic Q 065 RDO L INSTALLATION FOR PROGRAMMED CONTROL OF A MACHINE-TOOL I This invention relates to the programmed control of machine tools, and particularly relates to and concerns automatic equipment for controlling the movements of movable members such as a workpiece support table, a table support carriage, a tool support, all in accordance with a machining program predetermined in terms of the dimensions of the workpiece to be formed.

These installations consist of, with respect to control of the movements of each moving part of the machine, a motor such as a hydraulic or electric motor for example, linked to a drive providing the movements of the member, such as a screw and nut drive, the running of the motor being subject to a programmer whose orders are given in response to a system for the detection of the exact positions which the moving member of the machine takes up, one after the other; in other words to a system for detecting the dimensions.

Systems exist for continuous detection of the dimensions, or for gradual detection or for sequential detection. The first of these systems are generally very costly. The second present the inconvenience of lacking flexibility and necessitating a great deal of time for adjustment, which reduces the profitability of their application, notably for operations of short duration. In fact, sequential detection systems of the simplest kind consist of a single direct contact mounted at the end of the travel of the moving member to be controlled, for example a stop or a cam having appropriate control, for example mechanical, electrical, electronic or hydraulic or even pneumatic, which determines the stopping of the organ and the programmed engaging of the next sequence. The encumbrance of these stops or cams and the difi'iculty of adjusting them in a precise manner limits, to a large extent, their capacity for being programmed and their flexibility of operation.

The primary object of the invention is to create a programmed control installation for a machine tool which does not present the above-mentioned inconveniences of the normal or prior art installations.

To achieve this, object in accordance with the invention, the installation which is of the type comprising, for each carriage, a feed control mechanism linked to a motor and a control system for the supply of the said motor, is noteworthy in that it comprises means for the detection of approach having average precision, for example of the order of 0.3 mm. by defect, such means being capable of covering on their own the extent of the total travel of the carriage, and means for the detection of the high precision stopping having accuracy of the order of 0.02 mm. The electrical supply control system for the motor is, by appropriate linking means, first of all subject to the means for detecting approach, the information supplied by these means for detection of approach causing the motor to be switched on and slowed down to a minimum constant speed at the same time as such means prepares the said connecting means such that the electrical supply control system is then subjected to the means for detection of the stop. The information supplied by these means for detection of the stop then causes the cutting off of the supply to the motor so as to ensure the accurate stopping of the carriage.

Given that the means for detecting the approach in such equipment do not have to supply precise information, they can be of a relatively rudimentary structure and, as a result, of low manufacturing cost. So far as the stop detection means are concerned, they only need to operate over an extremely reduced field, namely the area corresponding solely to the correction of the information supplied by the approach detection means with the result that, for example, a range of 1 mm. is very largely sufficient. In addition, their operation is much simpler than that of sequential detection systems and, moreover, the approach detection means are designed in such a manner that their programming element can be located outside the machine, this latter element not being put out of operation during any preparatory operation, which considerably increases the profitability of the installation.

The reliability of this type of equipment is also greater than that of installations with sequential control by cams or stops of the normal type, in view of the fact that there never is any occasion, during machining, to stop the machine tool, to remove and refit the protective arrangements for the detection system, in order to carry out the delicate adjustments for compensating for wear on tools.

In one embodiment of the invention, the approach detection means comprise a perforated multitrack tape according to the program to be carried out and a case of photosensitive elements, these two elements being supported, one by the carriage, and the other by the carriage support.

Such a perforated tape can be made at the study office without any difficulty, with an accuracy of the order of 0.3 mm. which is largely sufficient for perfectly correct functioning of the equipment. The machine is therefore not immobilized during this period of preparatory work which can be relatively long. However this is a piece of work which does not present any special difiiculties and, in addition, since the perforated tapes each correspond to a machining cycle they can easily be stored and reused for carrying out a new series of identical parts.

In a particular embodiment of the invention the means of approach detection comprise a rotating drum linked to the feed control mechanism and fon'ns a perforated screen mobile between a light source and photosensitive elements regularly distributed around the drum in a number corresponding to the accuracy required, and preselection means which can be programmed for the selective activating of the photosensitive elements, the apparatus being designed in'such a manner that one complete revolution of the drum covers a length of carriage travel much greater than the length of travel corresponding to the degree of precision of the first means of detecting approach.

In a particularly advantageous arrangement, the approach detection means are formed from means for counting the revolutions of the above-mentioned drum for the means of stop detection. In this particular arrangement the two detections, approach and accurate stopping, are thus effected by using the same device.

. In a more elaborate embodiment the installation also includes adjustable manual preselection means for the selective activating of the photosensitive elements of the stop detector as well as means of inversion to be used for placing the photosensitive elements such that they either depend on the programmed means for preselection or else depend on the adjustable means for manual preselection. Due to such means, it is possible to regulate the final detection by signs from a programmer with a view to obtaining an experimental and speedy finalizing of the stop dimension. In addition it is possible, at any moment in the automatic machining cycle, to modify the stop dimension, for example to compensate for tool wear, and this can be also done too from a desk at the programming unit. Finally, there is the possibility of immediately programming a preliminary cycle by comparison with the finishing cycle previously established to obtain the dimensions of the finished piece.

The invention will be better understood by reading the following description and examining the accompanying drawings which show, by way of nonlimiting example, some preferred embodiments of an installation for the programmed control of a machine tool according to the invention.

FIG. 1 shows in perspective a milling machine table fitted with a first embodiment of programmed control devices according to the invention;

FIG. 2 is on a larger scale and is a plan view with cutaways of the approach detector shown in FIG. 1;

FIG. 3 is a vertical section along the broken line IIIlIl of FIG. 2;

FIG. 4 is, on a larger scale, a vertical section along the line IV-IV of FIG. 3;

FIG. 5 is a view in longitudinal section, on a larger scale, of the accurate stop detector shown in FIG. 1;

' FIGS. 6 and 7 are transverse sections made, respectively, along lines VI-VI and VII-VII of FIG.

FIGS. 8 to 13 are views of the type similar to FIGS. 6 and 7, showing the members in different positions;

FIG. 14 is an electrical diagram of the installation for automatic programmed control comprising the detectors shown in FIGS. 1 to 7;

FIG. 15 shows, on a larger scale, with cutaways, a programming master and a control desk;

FIG. 16 is an electrical diagram of the manual control equipment;

FIG. 17 is a plan view of a workpiece to be machined and it shows the machining cycle programmed accordingly by the equipment of FIGS. 1 to 16;

FIG. 18 is an elevation view of the part shown in FIG. 17;

FIG. 19 is a similar diagram to that in FIG. 14 for another embodiment;

FIG. 20 is a view in longitudinal section of another embodiment of the precise stop detector;

FIGS. 21 and 22 are transverse sections respectively along lines XXI-XXI and XXII-XXII of FIG. 20;

FIGS. 23 to 26 are views of the type shown in FIGS. 21 and 22, showing the members in different positions;

FIG. 27 is an electrical diagram of an installation for automatic programmed control comprising the detector of FIG.

FIG. 28 is a view in longitudinal section of another embodiment of the precise stop detector;

FIGS. 29 and 30 are front views of the two coding elements of this detector.

The invention will now be described in its application to the programmed control of movements of a milling machine table 1 (FIG. 1) in two dimensions corresponding respectively to the longitudinal movements of said table on carriage 2 which supports it, and to the movements perpendicular to the preceding ones, of the said carriage on slide rails 3 of the bench 4 which supports it, but it would be applicable in like manner to the programmed control of the movements of a machine organ in three dimensions.

The systems of programmed control in each of the three dimensions are identical so that there will now be described in detail only one of them, for example that concerning the longitudinal movements of the table 1 (FIG. 1). The data information unit comprises in this instance two photoelectriccomplementary detectors, namely: an approach detector D1 and a 1 precise stop detector D2.

The approach detector D1, shown in detail in FIGS. 2 to 4, comprises a scanning head 11 with photosensitive elements and a tensioned perforated tape 12 which move, in relation to each other, during the longitudinal movements of the table 1. In the example, the scanning head is fixed to the carriage 2 by screws such as 13, while the perforated tape 12. is-fixed, at its two ends, by means of two screws with milled head 14, to two solid pieces 15 engaging in a groove 16 of T" section in table 1, and fixed in position by screws 17 cooperating with nuts 18 engaged in the base of groove 16 so that the perforated tape 12 is parallel to the longitudinal axis of the table, that is, to the direction in which this table moves on carriage 2.

The scanning head 11 comprises a case 21 (FIGS. 2 to 4) having a certain number (four in thisembodiment) of horizontal holes 22, 23, 24, 25 arranged one above the other perpendicularly to the perforated tape 12 and enclosing photosensitive tubes 26, 27, 28, 29 respectively. Holes 22 to 25 communicate, respectively, through calibrated orifices 32, 33, 34, 35

with a guide channel 37 in which the perforated tape 12 can a photosensitive tube 53 mounted in a hole 54 formed in the thickness of the lower wall of the case 21. This photosensitive tube acts as proof of illumination of lamp 42. The case 21 is closed by a removable cover 56 which is removed for any replacement of lamp 42.

The power supply wires for lamp 42 and those for the photosensitive elements 26 to 29 and 53 pass into a junction 67 mounted in a sidewall of case 21 and into a flexible sheath 68.

The perforated tape 12 has several (four in the embodiment) tracks P1, P2, P3, P4 which permit avoidance of any dangers from interference to the inversions in the direction of movement of table 1. These tracks are each formed by a continuous line traced on the perforated tape 12 located to the right of each of the photosensitive elements 26 to 29.

The perforations, such as 81, 82, 83, 84 and 85 on the tape are made by any appropriate means, for example a hand punch, in a manner which will be described below.

The control unit for the longitudinal movements of table 1 comprises, in standard manner, a screw (not shown) mounted for rotation in the table and engaging in a nut fixed in the carriage 2. The screw is provided with a vernier 111 (FIG. 1) and it is driven by a motor unit with hydraulic control 112 fixed to table I by means of a support 113. The motor of this unit is fed by a supply tube and a fluid return tube lodged in a flexible sheath 114 by the intermediary of a distribution system which allows the motor to be turned as desired in one direction or the other and at different speeds, notably at a rapid approach speed, at an operating speed, and at a slow speed prior to stopping.

The precision stop detector D2 is fixed on one end face of r the motor unit 112 (FIG. 5). This apparatus comprises a plate 117 on to which is fixed a cylindrical case 118 containing a boss 119 in which are mounted two ball bearings 122, 123 supporting a shaft 124 parallel to the shaft 125 of the motor unit 112. These two shafts are connected by notched belt control 126 which passes over a pulley 127 pinned to shaft 125 of the motor and over a pinion 128 pinned to the shaft 124. The multiplication ratio thus created between the two shafts is a function of the pitch of the screw moving table 1 forward. In the example being considered one turn of shaft 124 corresponds to an advance of l mm. of table 1. This belt transmission is protected by a box 129 fixed for easy removal to plate 1 17.

On the cylindrical case 118 is screwed an annular support 132 which has, distributed at regular intervals around its axis, a crown of IO sockets 133-0, 133-1, 133-2, 133-3 133-9 (see also FIG. 6) communicating with the inside of the annular support 132 by radial holes 134-0, 134-1, 134-2, 134-3 134-9 as well as another crown of 10 other sockets 135A, 135B, 135C 1351 (see also FIG. 7) communicating as well with the inside of the annular support 132 by their respective holes 136A, 136B, 136C 136].

In the sockets 133-0 to 133-9 are arranged respectively photosensitive tubes 138-0, 138-1, 138-2, 138-3 138-9 and, in similar manner, in sockets 135A to 135] are likewise lodged respectively photosensitive tubes 139A 139B, 139C 139]. These photosensitive tubes are preferably photoresistant cells or photodiodes.

The inner extremity of shaft 124 is fixed solid to a drum 142 mounted in the inside of the annular support 132 and enclosing an electric lamp 143 mounted in an insulating holder 144 itself fixed by screws such as 145 in the pierced base of the annular support 132.

To the right of the circular row of holes such as 134-0, 134-1 134-9 the cylindrical wall of the drum 142 has a series of four windows 146-147-148-- 149 of identical dimensions. The circumferential arrangement and dimension of these windows are such at any moment as it turns in one direction or the other the drum 142 permits illumination of four photosensitive elements during a rotation of an angle 1a, 2a, 3a, 4a then their occultation during a rotation of an angle d. In the example chosen the angle 0 corresponds to a linear movement of the controlled table of 0.02 mm. In other words, for this embodiment, the establishing of the final dimension can be effected with a maximum deviation 01'1001 mm. with reference to the actual dimension required.

To each window naturally correspond two multiple apertures blocking angle a and corresponding to the two directions of rotation of the drum 142 (see FIGS. 8 and 9). The peripheral length of the window is a function of the definition chosen and the diameter of sighting of the photosensitive elements. Thus, if a represents the minimum angle of control movement (or definition, here 0.02 mm.) and c the angle of sighting of the photosensitive elements (angle at which the radial holes 134/0, 13:1/1 134/9 are seen from the center 0) the angular aperture A of each window is equal to:

The three full parts which separate among themselves the four windows 146, 147, 148, 149 have a peripheral length of F2+cc+a(5ac)=6a+c To the right of the other circular row of holes such as 136-A, 136-B 136-] the drum 142 presents a wide opening 151 leaving one part whole or masked 152 (FIGS. 7 and 10) whose axis of symmetry coincides with that of part 150 of the drum to the right of the row of holes 134-0, 134-1 134-9 (FIG. 11).

We shall call b the angle formed by the axes of sighting of two photosensitive elements which are consecutive. Angle b corresponds to a linear displacement of the controlled table of =0.l mm. (b=5a). The mask 152 is designed to determine an angular clearance of the drum 142 of 50 when the other stage of detection (FIG. 6) can determine at any time an angle rotation of value a, 2a, 3a, or 4a.

The peripheral dimension and the angular adjustment of the mask 152 also permits the completing from an angle a (in the two directions of rotation of the drum l42-FIG. 11) the last controlled position by the stage in FIG. 6.

According to a simple electrical diagram, as will be explained later, the stopping of motion can be determined by the total occultation of the sighting apertures of the programmed elements. In this embodiment, to permit an experimental adjusting of the machining dimension, there is therefore good reason for programming two sets of data of which one defines the 0.1 mm. and the other the 0.02 mm.

Since a first approach detection has permitted the establishment of the dimension by default to some tenths and hundredths of a mm. almost, it is easy to determine the actual dimension bearing in mind the effects of mechanical, electrical and hydraulic inertia of the whole of the control and command elements for the controlled table.

In the present instance it is supposed that the angle a is less than angle 0 (FIG. 12 but the same ratios would be applicable in an embodiment where angle a was, on the contrary, greater than angle 0, such as shown in FIG. 13 relative to a variation in which angle a has in any case a different value from that in the embodiment shown in FIG. 12. In the instance mentioned it is supposed that the excess travel due to the inertias is in the order of 0.1 mm. That is why it is necessary to arrange, for the stage controlling the 0.02 mm., occultation masks d (FIG. 11) whose angular adjustment is translated by a table displacement greater than 0.1 mm. This occultation prolonged beyond the excess stop travel is one of the important features of the invention. It permits the programming of the application of a simple electric control circuit of the sequential type.

At each 0.1 mm. of the stage in FIG. 7 it is possible to program alternatively to complete to 0.02 mm., 0.04 mm., 0.06 mm. or 0.08 mm. one of the four photosensitive elements in even order and then one of the four photosensitive elements in odd order of the stage in FIG. 6. The operator thus has available one window with continuous illumination with a maximum dimension of 0.78 mm. and adjustable by 0.02 of a mm. from zero.

It can be supposed, by way of example, that by default the first detection D1 positions the controlled table at a point such that the drum of detector 142 occupies the position shown by FIGS. 8 and 10.

The operator reads on the vernier 111 (FIG. 1) the dimension attained and sees that there is still 0.14 mm. to be travelled, for example, in order to attain the desired dimension. He has available vernier to let him know at this moment the position of the internal drum 142 and, in addition, a graph which has been specially drawn up enabling him to know a priori the combinations to put into operation manually (by means of rotators), that is to carry out manually the adjustment of the precise stopping of the second detector D2.

In the example under consideration, it is necessary to program the combination 139-1 (FIG. 7), 138-6 (FIG. 6) so that after occultation of the photosensitive element 139-1 and the photosensitive element 138-6 the drum 142 has turned through an angle representing the movement of 0.l4 mm. desired. The graph which the operator has takes account of the average response time of the different movements which can be carried out on the machine under consideration. It is therefore very possible that this first attempt does not allow the attainment of the rigorous dimensions required in view of the possible peculiarities of the parameters of inertia operating at the dimension and displacement desired.

There will then be grounds for reading again the vernier 111 (FIG. 1) of the machine for the position attained by the controlled table and on vernier 165 the position occupied by drum 142. All that remains to be done is to correct once again the message so that the second detector D2 is conditioned for stopping at the close dimension.

The interest of the device therefore lies in being able to carry out experimentally under the same conditions as will operate during the automatic cycle the manual adjustment of the positioning obtained in successive approximations.

The control of the luminosity of the lamp 143 is effected by a photosensitive tube 161 mounted in a radial hole 162 of the base of the annular support 132 communicating with the interior of this support by a hole 163 in the longitudinal direction. Thus, when lamp 143 is lit, its illuminating rays are reflected on the internal base of the rotating drum 142 and reach the photosensitive tube 161 through hole 163.

A stopper 167 screwed on to the box 118 closes the whole of the unit in moisture-tight manner due to the presence of a joint 168.

In FIG. 14 there has been shown schematically the main part of the system of automatic control associated with the detectors described above. In this sketch will be found detector D1 and its four photosensitive cells 26, 27, 28, 29 capable of being stimulated through perforations in the tape 12 by lamp 42; the detector D2 with its 10 photosensitive cells 139A to 139] and its 10 photosensitive cells 138-1 to 1238-11; and the motor unit 112 for controlling the feed screw for table 1 as well as a motor unit 112A for driving the control screw for the feed of carriage 2.

The detector D1, through the intermediary of a contact RIB of a relay R1 stimulates the coil 174 of a selector 172 of any appropriate standard type having as many preselection contact studs as the device itself is fitted with possible sequences of machining.

The selector 172 serves to supply successively columns (of which the first 11 have been enumerated in the drawing) of a matrix 171 utilizing plug-in diodes 200 (see also FIG. 15). The horizontal lines of this matrix correspond to the different parameters of all the possible sequences, namely, in the example: longitudinal movement of the table to the right, longitudinal movement of the table to the left, transverse movement of the table forwards (that is corresponding movement of the carriage supporting the table), transverse movement of the table backwards, then fast speed, working speed, slowing.

down speed, then the selection of the four tracks of the tape, selection of the 10 photosensitive cells 139A to 139] and finally the selection of the 10 photosensitive cells 138-1 to 138-0. The last line of the matrix shown as D2 plays a special role to which reference will be made later.

The outlets of the different lines on the matrix correspond to the parameters shown, namely the first line to the stimulation of an electrovalve 176 for supplying the motor unit 112 with longitudinal movement of table I to the right, the second to the same electrovalve 176 stimulated in the other direction, the third and fourth lines to stimulation of an electrovalve 177 for supplying the motor unit 112A, in one direction or the other. for movements of the carriage 2.

The outlet of the line marked fast speed" is linked to two electrovalves 182 and 183. Electrovalve 182 conditions the direct intake of the motor units 112, 112A. Electrovalve 183 in its neutral position, as shown, fills pump 192 directly from the tank. Stimulation of coil 1830 of this valve causes the closing of the release circuit and forces the whole supply in the pump to drive motors 112 or 112A.

The outlet of the line marked working speed" is linked to coil 18312 of electrovalve 183 which then forces a part of the pump supply to pass through a flow regulator which can be adjusted 188 on its way back to the tank so that the other part of this supply, likewise variable, is led to the motors 112, 112A.

The outlet of the line marked slowing down speed" is linked to an electrovalve 184 by the intermediary of a shutoff contact R1C of the relay R1 which pilots the flow regulator 188 in the direction ofits maximum opening.

The outlets from the four lines corresponding to the four tracks P1, P2, P3 and P4 of the perforated tape are linked respectively to the four photocells 26, 27, 28, 29.

The outlets of the twenty lines A, B, C J and 1,2,3.... 9,0 are linked respectively to the corresponding photocells l39-A, 139-B 139-] and 138-1, 138-2, 138-9, 138-0, respectively.

The outlet of the last line D2" is linked to the stimulation coil of a relay R2 for activating a reversing contact R2A.

In the drawing in FIG. 14 there has once again been shown: a liquid reservoir 191, a pump 192, an electric motor 193 for driving this pump, a safety release valve 194.

In FIG. 15 there has been shown, apart from the matrix 171, a control panel 221 on which are found, for adjustment by manual control of the machine, an inching lever 222 for controlling movements of the table and the carriage in one direction or the other, a selector for fast speed or working speed 223, a pushbutton 224 for controlling the switch to minimum speed, an inverter 225 whose function will be explained later, a track selector 227, a selector for correction in tenths of millimeters 228, and a selector 229 for correcting to 0.02 mm. Also shown is a handle 232 entitled Manual search of sequences by means of which it is possible to move the selector 172 forward, step by step, at any time.

Two pilot lights 234, 235 show together the number of order of the sequence to which the inching selector 172 is connected.

FIG. 61 depicts an electrical diagram relating to the control panel 221 whose components have just been described. On it are found the same member designated by the same reference numbers. The inching lever 222 serves to lock in the different live positions contacts 222/l, 222/2, 222/3 or 222/4 respectively.

Programming of the precise stop by detection D2 of the 7 controlled movement and of the start of the following movement are carried out plugging in diodes such as 200 (FIG. 15) into the matrix 171 for control of the automatic cycle or by simple manipulation of the three turning buttons 227,228, 229 for so-called manual control of adjustment.

There will now follow, in the first instance a description of automatic control, taking as an example sequence 2 whose signalling and detection circuit are shown in FIG. 14. By standard utilization of the matrix 171, supply current 225/1 vertically distributed by selector 172 is switched horizontally in accordance with the signal, on one hand on to the photoelectric cell 26 of the detectors D1 and, on the other hand on to the photoelectric cells 139-B and 138-1 of the detectors D2.

These different photoelectric cells allow the current 225/1 to pass when they are illuminated: note should be taken of their method of connecting in parallel. The chronological functioning of the two detectors is as follows: in the first stage,

the movement being programmed by a longitudinal movement to the right at fast speed with slowing down at the end, the corresponding control means. brought into operation as already described, determine the movement of table I.

The movement of this table displaces the perforated tape 12 of the detector D1 in such a manner that a predetermined perforation on track P1 allows, at a particular moment, illumination of the photoelectric cell 26.

As a result, current 225/l, released at this moment, reaches the amplifying relay R1 (FIG. 14) whose contacts RlA, RIB,

RIC close; the autosupply contact RlA switches on, to the control circuit of the relay R1, a maintenance current from the detector D2 operating at that moment.

The direct supplying of the amplifying relay R1 by circuit 186 is maintained until total occultation of the lighting of the cell 26 and, by means of the autosupply circuit 185, this relay stays under supply until the total occultation of the photoelectric cells 13913 and 138-1 of detector D2.

As has been already explained the different windows of the drum 142 at the stages in FIGS. 6 and 7 of the detector D2 make it possible to maintain illumination of the two photoelectric cells chosen angularly in a fixed and accurate manner in space with relation to the turning masks for final stopping of the sequence then running. The programming matrix 171, by its first seven horizontal lines 171-1 (FIG. 15) makes it possible to control the control means of the motor units 112 and 112A and by its following 24 horizontal lines 171-2 makes it possible to ensure, at precise moments in time, the cutting in and out of the amplifying circuit R1.

This relay includes, independently of the autosupply circuit RlA, the two circuits controlled by its shutoff circuits RIB and RIC.

Upon switching in of the amplifying circuit R1 the contact RlB charges the electromagnet 174 which prepares the inching selector 172. Upon switching out of the relay R1 the electromagnet 174 is once again uncharged and the ratchet mechanism is recalled by spring 187 which causes the selector to move forward one step, from position 1 to position 2, for example, cutting off the supply to the functions programmed in column I in order to control those of column 2. Thus each switch out of the amplifying relay R1 causes successively the feed from left to right the feeding of each column of the programming matrix (FIG. 15) whose switching into circuit is shown by tubes 234 and 235 (for example No. 1 in the position of the selector 172 shown in FIG. 14). Upon switching in of amplifying relay R1, the contact RIC also closes and, if a slowing down is programmed on the matrix for sequence No. 2, a supply current 225- 1 reaches, at this moment in the sequence, the electrovalve 184 which pilots the flow regulator 188 controlling the reduced forward feed of the final travel.

.The last horizontal line 171-3 designated D2" on the matrix has as its function the control of the relay R2 which switches the circuit 185 to direct control of the amplifying relay R1. This permits increasing the correction capacity of the detector D2. In fact, in the proposed embodiment, the maximum dimension of the illuminating window is 0.78 mm. which can sometimes be too limited. If, for example, after carrying out the maximum correction, the dimension is still not attained, one simply needs to program a new sequence with the same data as the previous one, but with D2 signalled to obtain a movement of 1 mm. more (total capacity of detector D2). Thus, by this detection of every turn of detector D2 corresponding to 1 mm. travel of the table, a new sequence is initiated and an accurate dimension can be obtained at several millimeters distance through counting by means of the selector 172 and with final detection as previously described.

For operating with manual control of the programming of the device, the operator has a desk 01 panel 221 (FIGS. 15 and 16) which allows him to search thesignalling of the corrections to be made, sequence by sequence, to the approach detection D1 so as to ensure the accurate dimension of machining. On this desk, the two-way switch 225 distributes, in a distinct manner, a supply current when the button is placed in position 225-l of the automatic cycle." The selector 172 is fed as has been described previously and shown in FIG. 14. If this same switch is placed in position 225/2 of the manual cycle it distributes a supply current 225/2 to the inching selector 172, on another distribution stage from the previous one, and to the turning buttons 227 228 229 according to FIG. and as illustrated in FIG. 16.

The operator can then simulate all the functions of a sequence from the buttons 222 223 224 (FIG. 15) which controls the command of the motor units 112 and 112A.

The manipulator 222, operated in instinctive manner according to the 4 directions 222/] 3A4, controls the electrovalves for distribution 176 and 177 (FIG. 16) at fast and working speed, depending on the position of the turning button 223 with the possibility of slowing down at the end of travel by switching off button 224.

The table, now controlled manually by operating manipulator 222, is directed in the proposed direction of machining, for the sequence intended, and drives the perforated tape 12 for approach detection, in such a way that a predetermined perforation on the track chosen by the turning button 227 (FIGS. 15 and 16) enables the illumination of the photoelectric cell switches on to control the amplifying relay R1. In addition, and in the same way, the turning buttons 228 and 229will simulate the operation of the matrix for signalling the combinations for final detection of the controlled detector D2. Once the operator has simulated the automatic functioning of a sequence by means of the desk pushbuttons he can control this whole sequence by keeping closed one of the contacts '222/l-B2-3 or 4. At the end of travel, after switching out the amplifying relay R1, selector 172 advances one stage and cuts the supply 225/2 to all the control and detection elements (FIG. 16). Halting of the controlled table having now taken place, the operator can check the dimension attained from the vemier 111 of the table.

To enable a new start by table I or carriage 2, it is necessary to maneuver button 232 which moves forward by a new stage, the selector 172 for a new supply 225/2 to the command and control elements on desk 221. It will be noted that supply to the elements in response to the operation of button 232 through the intermediary of selector 172 is ensured only in one stage of two of the selector so that the release of one end of sequence causes the stopping of the table even if the button for manual control 232 is kept in the operating position. In addition, given the fact that the manual control of the machine activates the same electronic and electric components (notably the step by step advance selector 172) as the control in automatic cycle, the adjustment of the precise stops takes place accordingly in the same circumstances, notably the conditions of inertia, for release of the sequences.

Manual control of button 232 also allows the moving forward of the selector 172 as many stages as is necessary for searching for a determined sequence still signalled by the indicator tubes 234 and 235. After manual adjustment of a sequence with the help of desk 221, the operator can report by pins all the driving information on one column of the matrix 171 and position, with the aid of button 232 and indicators 234, 235, selector 172 for carrying out this sequence. When the switch is turned to 225 automatic cycle, the whole of the programming is then conditioned and the tested manual sequence is repeated automatically. Step by step, using successively the desk 221 and the matrix 171, the operator can carry out a machining cycle prepared in the Methods Office and regulated with accuracy from the programmer (without interfering with the machine or the detector D1). This cycle can be readjusted by means of the matrix, at any time for example to compensate for tool wear or to correct any kind of displacement.

With a view to maintaining the adjustment made on the matrix, for subsequent manufacture of another series of parts, it is possible, on a roll on which are printed the columns and lines of the matrix, to make perforations at the positions of the pins so that, to carry out the manufacture of a new series of parts, it will be necessary only to place the perforated roll on to the matrix and to push a pin into each hole in the roll, the pin thus ensuring the corresponding links with the matrix. The roll stays in place during operation.

The functioning of the unit will now be explained with reference to the machining of a workpiece of the type shown in FIGS. 17 and 18. This piece, shown in its entirety by 201, is a support incorporating a flange 202 which is to remain rough and, projecting from this flange, on one hand, two slides, 203, 204 having respectively a flat horizontal face 205, 206, in a common plane and two flat parallel vertical faces 207, 208. The flange 202 also has a raised edge 211 presenting a transverse vertical face 212 and a small horizontal face 213. The machining of this piece therefore includes successive truing operations carried out by means of a vertical milling cutter 215, namely: truing of the horizontal face 205 and the vertical face 207 of the slide 203, truing of the vertical face 212 and the horizontal face 213 of the raised edge 211, and finally, truing of the horizontal face 206 and the vertical face 208 of the slide 204.

The workpiece 201 is secured, flat, on the table of the machine in such a way that the slides 203 and 204 are parallel to the longitudinal axis of the table.

F 0 indicates the position of the milling cutter 215 at the start of the machining cycle. The height of the cutter and the position of the table on the transversal carriage 2 are such that the first longitudinal move forward of table 1, in the direction of the arrow fl effects the truing of the horizontal face 205 and the vertical face 207. This movement of the table must be made at a speed equal to the feed speed of the work. As soon as the milling cutter is lifted'from the surface 205 which it has just machined, that is, when it occupies the position Fl, the table of the machine can assume a fast speed as far as the vicinity of position F2, then a slow speed to stop exactly at this point, corresponding to the machining of the vertical speed 212 and the vertical face 213 of the workpiece by displacement of the transversal carriage 2. It is supposed that the horizontal face 213 is at the same level-as that of the faces 205 and 206 of the two slides to be machined so that, for the example in question, there is no need to consider vertical movement of the table or the cutter.

The principle would be the same if it were necessary to add such a movement.

After machining of the faces 212 and 213, the cutter is located in position F3 in relation to the workpiece. The table will now move in the direction counter to arrow fl at fast speed until the cutter is in position F4. The speed of the table is then reduced and corresponds to the machining speed for truing of the horizontal face 206 and the vertical face 208. The cutter then reaches position F5 and the table speed can, once again, be increased until the cutter reaches the position F6 from which, by a transverse movement of the carriage in the direction of the arrow f2 the cutter reaches position F7, that is, it is once again in the first position F0 of the start of the cycle.

It will be noted that the second, third and seventh sequence, at the end of which the cutter should occupy respectively positions F2, F3-and F7 are the only ones for which the position of the workpiece must be determined with great accuracy since they determine the positioning of the vertical face 212, the vertical face 208 and the vertical face 207 (for the following cycle) respectively. In fact, the points Fl F4, F5 at which the speed of the table must be modified in the longitudinal direction and point F6 where it has to be stopped at the end of a cycle, have absolutely no need tobe accurate since they do not determine any machining dimension of a face on the workpiece.

The result is that, for the first seven sequences of the cycle in question, although the approach detector D1 must obviously be used for each sequence, the precision detector D2 will not require to come into action except for ascertaining the positions F2, F3, and F7. 

1. An installation for positioning a movable element of a machine-tool along a predetermined path, said installation comprising drive means including a rotatable lead screw coupled to said element, drive speed control means, stop means to discontinue the drive and stop said element when said element reaches a desired position along the path, a course positioning control including means for detecting a first position of said element ahead of said desired position and for detecting a second position of saId element between said first position and said desired position thereof, a fine positioning control including means coupled to said lead screw for producing within a full revolution thereof a control signal beginning when said element reaches a position intermediate said first and second positions and ending when said element reaches said desired position thereof, and actuating means for said drive speed control means and for said stop means, said actuating means being responsively coupled to said detecting means and being operable to cause said drive speed control means to reduce the drive speed when said detecting means detect said first position of the movable element and to condition said stop means to discontinue the drive when said detecting means detect said second position of the movable element, said control signal of said fine positioning control being coupled to said actuating means and being effective to override and prevent said actuating means from discontinuing the drive when said element reaches said second position and to allow said actuating means to stop the drive when said element reaches said desired position thereof.
 2. An installation as claimed in claim 1, in which said fine positioning control includes a roll of fixed photosensitive elements selectively connected to an electrical circuit linked to a supply control device for said motor as a function of the exact position at which said carriage is to stop after slowing down in response to said course positioning control and, (b) at least one control window carried by a rotating mobile coding element between a light source and said roll of photosensitive elements and linked to said mechanism for controlling the drive to the carriage.
 3. An installation as defined in claim 1, in which said course positioning control includes a perforated tape having several tracks based on the programs to be carried out, and a case of photosensitive elements, said tape and said photosensitive elements being carried, one by said carriage and the other by said carriage support.
 4. An installation as defined in claim 1, in which said fine positioning control comprises a rotating coding element linked to said mechanism for controlling the drive and forming a moving aperture screen between a light source and photosensitive elements set at regular intervals in relation to said rotating coding element in a number corresponding to the precision required, and programmable means of preselection for the selective activating of said photosensitive elements, the whole unit being designed such that a complete revolution of said rotating coding element covers one length of travel of said carriage largely greater than the length of travel corresponding to the degree of precision of said course positioning control.
 5. An installation as claimed in claim 4 in which said course positioning control includes means for counting the revolutions of said rotating coding element of said fine positioning control.
 6. Installation as claimed in claim 5, in which said rotating coding element itself produces, with each revolution, an impulse for controlling the drive of a counter.
 7. Installation as claimed in claim 4 additionally including adjustable manual means of preselection for the selective activating of said photosensitive elements of said fine positioning control means, and means of inversion for selectively placing said photosensitive elements either in a state of dependence on said programmed preselection means or in a state of dependence on said adjustable manual means for preselection.
 8. Installation as claimed in claim 7, in which the adjustable manual means for preselection for the selective activating of the said photosensitive elements are made up of switches inserted into the supply circuits for said photosensitive elements.
 9. An installation for programmed control of a machine-tool of the type comprising, for each carriage, a mechanism for controlling the drive link to a motor and a system fOr controlling the supply to said motor, said installation including means for the detection of approach having a relatively average accuracy of the order of 0.3 mm., by default, said approach detection means being capable of covering on their own the total these two pitches having a single interval of circumferential length substantially equal to that of the mask of the first stage of detection.
 10. Installation as claimed in claim 9, in which each of the two stages comprises 10 photosensitive elements which are equidistant, the mask of the first stage extending over an arc covering two successive intervals between two photosensitive elements, the angle of the phase displacement of the lights of the second stage being equal to a fifth of the angle between two successive photosensitive elements, and the angle of the longest part between the windows of the second stage being equal to the angle of the mask of the first stage increased, at each of its two ends, by the angle of the displacement of phase, the photosensitive elements in odd order or those in even order in the second stage being selectively put into service condition according to whether the mask of the first stage is working itself in conjunction with a photosensitive element of odd or equal order.
 11. An installation as claimed in claim 10, in which one revolution of the rotating coding element corresponds to a move forward of 1 mm. of the controlled member, the angle between two successive photosensitive elements being equal to one-tenth of the circumference corresponding to a travel of 0.1 mm. of the controlled member and the angle of displacement of phase being equal to one-fiftieths of the circumference corresponding to 0.02 mm. advance of the controlled member.
 12. An installation as claimed in claim 7, in which the means for counting the revolution of the rotating coding element include a counting unit set at each sequence for a predetermined number of revolutions programmed by adding a signal to the matrix, the backwards count of this counting unit taking place in response to the impulses at each revolution of the rotating coding element, and wherein the adjustable manual means of preselection include a set of switches for setting the counting unit to any number of revolutions desired.
 13. An installation as claimed in claim 2, in which the first stage of detection includes a number of equidistant photosensitive elements one-fiftieth a mask extending over an arc covering at least one successive interval between said photosensitive elements, and wherein the windows of the second stage of detection are equidistant and the photosensitive elements of the second stage detection are arranged according to a spacing smaller than that of said windows to the value of an angle of displacement of phase equal to one-fiftieth of the circumference corresponding to 0.02 mm. advance of the control member and distributed over an arc less than 360*.
 14. Installation as claimed in claim 13, in which the arc covered by said mask corresponds to several said intervals.
 15. Installation as claimed in claim 13 including more than two stages of detection, the additional stages being supplemental and having a finer or larger definition than the second stage of detection mentioned.
 16. Installation as claimed in claim 13 in which the number of photosensitive elements in the second stage of detection is equal to the number of corresponding windows in the rotating coding element.
 17. Installation as claimed in claim 2, in which the width of the windows of the rotating coding element is determined as a function of the inertia of the movement control of the member driven by the machine.
 18. Installation as claimed in claim 2, in which the rotating coding element is in the form of a disc and its windows are formed from holes made in this disc on a same circumference.
 19. Installation as claimed in claim 9, in which, against the mask, counter-maSk is applied having the same profile as the mask and which has, in addition, a row of windows identical to those of the second stage of the rotating coding element of detection, said counter-mask being fixed to the mask in an angularly adjustable manner to permit the reduction of the effective width of the above-mentioned windows as a function of the inertia of the movement control of the corresponding carriage.
 20. An installation for programmed control of a machine-tool of the type comprising, for each carriage, a mechanism for controlling the drive link to a motor and a system for controlling the supply to said motor, said installation including means for the detection of approach having a relatively average accuracy of the order of 0.3 mm., by default, said approach detection means being capable of covering on their own the total extend of travel of the carriage; and means for the detection of stopping having a relatively high accuracy of the order of 0.02 mm; and wherein said system for controlling the supply to said motor is connected through appropriate connecting means to selectively be commanded by said approach detection means, the information extent of travel of the carriage; and means for the detection of stopping having a relatively high accuracy of the order of 0.02 mm.; and wherein said system for controlling the supply to said motor is connected through appropriate connecting means to selectively be commanded by said approach detection means, the information supplied by said approach detection means causing the supply of current to said motor to change so as to slow down said motor to a constant minimum speed and at the same time conditioning said connecting means so that said supply control system is put under the control of said stop detection means, the information supplied by said stop detection means subsequently causing cutting off of said supply to the motor in order to ensure the precise stopping of said carriage, and in which the rotating coding element has at least two stages of detection, a first stage which includes, to the right of a first annular roll of photosensitive elements, a mask extending along a circumferential length greater than that corresponding to the angle of rotation of said rotating coding element which is driven by inertia after the control signal for precise stopping, and a second stage including, to the right of a second annular roll of photosensitive elements, several windows whose pitch is of an angle, in relation to the pitch of said corresponding photosensitive elements, of phase displacement equal to the smallest unit which it is desired to control, i.e., an angle corresponding to the definition which it is desired to obtain in stopping the control member, by substantially forming a vernier with one of supplied by said approach detection means causing the supply of current to said motor to change so as to slow down said motor to a constant minimum speed and at the same time conditioning said connecting means so that said supply control system is put under the control of said stop detection means, the information supplied by said stop detection means subsequently causing cutting off of said supply to the motor in order to ensure the precise stopping of said carriage, and wherein said programmable preselection means for the selective activating of said photosensitive elements includes a matrix the columns of which are supplied successively by a step-by-step selector switch placed in a state of dependence on said approach detection means, the lines of this matrix being placed, respectively, into circuit for supplying said photosensitive elements, preselection being determined by the positioning of pins pushed into the involved points of intersection of the columns and the lines of the matrix. 